Fabric Heats Up and Cools Down its Wearer

Calendar October 18, 2022 | Posted by admin

Textile engineers have developed a fabric woven out of ultra-fine nano-threads made in part of phase-change materials and other advanced substances that combine to produce a fabric that can respond to changing temperatures to heat up and cool down its wearer depending on need. The material that can store and release large amounts of heat when the material changes phase from liquid to solid. Combining the threads with electrothermal and photothermal coatings that enhance the effect, they have in essence developed a fabric that can both quickly cool the wearer down and warm them up as conditions change.

Such fabrics often make use of phase-change materials (PCMs) that can store and later release large amounts of heat when the material changes phase (or state of matter, for example, from solid to liquid). One such material is paraffin, which can in principle be incorporated into a textile material in different ways. When the temperature of the environment around the paraffin reaches its melting point, its physical state changes from solid to liquid, which involves an absorption of heat. Then heat is released when the temperature reaches paraffin’s freezing point.

 

“The problem here has been that the manufacturing methods for phase-change micro-capsules are complex and very costly,” said Hideaki Morikawa, corresponding author of the paper and an advanced textiles engineer with the Institute for Fiber Engineering at Shinshu University. “Worse still, this option offers insufficient flexibility for any realistically wearable application.”

So the researchers turned to an option called coaxial electrospinning. Electrospinning is a method of manufacturing extremely fine fibers with diameters on the order of nanometers. When a polymer solution contained in a bulk reservoir, typically a syringe tipped with a needle, is connected to a high-voltage power source, electric charge accumulates on the surface of the liquid.

A paper describing the manufacturing technique appeared in the American Chemical Society journal ACSNano.

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Artificial Skin Opens SuperHuman Perception

Calendar January 29, 2019 | Posted by admin

A new type of sensor could lead to artificial skin that someday helps burn victims ‘feel’ and safeguards the rest of us, University of Connecticut (UConn)  researchers suggest in a paper in Advanced Materials.

Our skin’s ability to perceive pressure, heat, cold, and vibration is a critical safety function that most people take for granted. But burn victims, those with prosthetic limbs, and others who have lost skin sensitivity for one reason or another, can’t take it for granted, and often injure themselves unintentionally. Chemists Islam Mosa from UConn, and James Rusling from UConn and UConn Health, along with University of Toronto engineer Abdelsalam Ahmed, wanted to create a sensor that can mimic the sensing properties of skin. Such a sensor would need to be able to detect pressure, temperature, and vibration. But perhaps it could do other things too, the researchers thought.

“It would be very cool if it had abilities human skin does not; for example, the ability to detect magnetic fields, sound waves, and abnormal behaviors,” said Mosa.

Mosa and his colleagues created such a sensor with a silicone tube wrapped in a copper wire and filled with a special fluid made of tiny particles of iron oxide just one billionth of a meter long, called nanoparticles. The nanoparticles rub around the inside of the silicone tube and create an electric current. The copper wire surrounding the silicone tube picks up the current as a signal. When this tube is bumped by something experiencing pressure, the nanoparticles move and the electric signal changes. Sound waves also create waves in the nanoparticle fluid, and the electric signal changes in a different way than when the tube is bumped.

The researchers found that magnetic fields alter the signal too, in a way distinct from pressure or sound waves. Even a person moving around while carrying the sensor changes the electrical current, and the team found they could distinguish between the electrical signals caused by walking, running, jumping, and swimming.

Metal skin might sound like a superhero power, but this skin wouldn’t make the wearer Colossus from the X-men. Rather, Mosa and his colleagues hope it could help burn victims “feel” again, and perhaps act as an early warning for workers exposed to dangerously high magnetic fields. Because the rubber exterior is completely sealed and waterproof, it could also serve as a wearable monitor to alert parents if their child fell into deep water in a pool, for example.

Source: https://today.uconn.edu/

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